Molecular and General Genetics MGG

, Volume 254, Issue 4, pp 400–406

Genetic evidence of a coupling role for the TraG protein family in bacterial conjugation

  • E. Cabezón
  • J. Ignacio Sastre
  • F. de la Cruz
ORIGINAL PAPER

DOI: 10.1007/s004380050432

Cite this article as:
Cabezón, E., Sastre, J. & de la Cruz, F. Mol Gen Genet (1997) 254: 400. doi:10.1007/s004380050432

Abstract

The ability of conjugative plasmids from six different incompatibility groups to mobilize a set of mobilizable plasmids was examined. The mobilization frequencies of plasmids RSF1010, ColE1, ColE3, and CloDF13 varied over seven orders of magnitude, depending on the helper conjugative plasmid used. Mobilization of CloDF13 was unique in that it did not require TrwB, TraG or TraD (all members of the TraG family) for mobilization by R388, RP4 or F, respectively. CloDF13 itself codes for an essential mobilization protein (MobB) which is also a TraG homolog, only requiring a source of the genes for pilus formation. Besides, CloDF13 was mobilized efficiently by all conjugative plasmids, suggesting that TraG homologs are the primary determinants of the mobilization efficiency of a plasmid, interacting differentialy with the various relaxosomes. Previous results indicated that TraG and TrwB were interchangeable for mobilization of RSF1010 and ColE1 by PILW (the pilus system of IncW plasmids) but TraG could not complement conjugation of trwB mutants, suggesting that additional interactions were taking place between TrwB and oriT(R388) that were not essential for mobilization. To further test this hypothesis, we analyzed the mobilization frequencies of ColE1 and RSF1010 by the P, W, and F pili in the presence of alternative TraG homologs. The results obtained indicated that the frequency of mobilization was determined both by the particular TraG-like protein used and by the pilus system. Thus, TraG-like proteins are not generally interchangeable for mobilization. Therefore we suggest that the factors that determine the frequencies of transfer of different MOB regions are the differential interactions of TrwB with pilus and relaxosome.

Key words Plasmid mobilization  IncW plasmid R388  TrwB   TraG  Plasmid CloDF13

Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • E. Cabezón
    • 1
  • J. Ignacio Sastre
    • 1
  • F. de la Cruz
    • 1
  1. 1.Departamento de Biología Molecular, Universidad de Cantabria, C. Herrera Oria s/n, E-39011 Santander, SpainES